1. Field of the Invention
This invention relates to a cap for use with a medical tool connector. More particularly, it relates to a cap for use with such a medical tool connector as a connector of the type to be fitted to the leading end of a tube extended as a connector from a dialytic liquid bag which is used as in the method of peritoneal dialysis, for example.
2. Description of the Prior Art
In the mutual connection of tubes or in the connection of a tube to a container or to a catheter involved in preparation for the continuous therapy such as peritoneal dialysis, solution transfusion, or blood transfusion, perfect prevention of the tube interior from ingression of microorganisms poses itself a technical task. Particularly in the peritoneal dialysis, a therapy to be performed at such a site as the abdominal cavity which has absolutely no ability to protect against microorganisms infallible prevention of the ingression of microorganisms through the tube into the abdominal cavity is regarded as an absolute technical task. The latest therapy by peritoneal dialysis is such that the apparatus and tools to be used therefor are not voluminous and the cost incurred thereby is conspicuously small as compared with the dialysis resorting to an artificial kidney. Since the cause for peritoneal coalescence has been substantially elucidated, the peritoneal dialysis can be performed without inducing peritoneal coalescence. Moreover, the therapy itself has been developed to the extent of appreciably lowering the burden exerted on the patient. Further, the method of continuously applicable peritoneal dialysis (CAPD method) which allows the patient to take an uninterrupted treatment while continuing his work has been invented and employed widely for practical use. In these advantageous circumstances, this therapy has been reawakening interest and attracting attention. The reliability of this method of dialysis with respect to the safety of life hinges on the question as to whether or not the ingression of microorganisms such as bacteria and viruses into the tube can be infallibly prevented and, consequently, the complication of peritonitis due to the propagation of such microorganisms within the abdominal cavity can be avoided. It is held at present that protracted performance of this therapy is not completely feasible.
As a typical example, the conventional method of continuously applicable peritoneal dialysis will be described below. By a surgical operation, a catheter is implanted in a patient's abdominal cavity and a connector member is attached to the extracorporeal end of the implanted catheter or the catheter having the connector member is attached in advance thereto is wholly implanted in the patient's abdominal cavity. Then, a connector member attached to the leading end of a tube of a dialytic liquid bag is connected to the connector member of the implanted catheter either directly or through the medium of a tube having connector members attached one each to the opposite ends thereof. The bag is suspended at a prescribed height higher than the abdominal cavity so that the dialytic liquid contained in the bag will flow down into the catheter and induce the dialysis aimed at. In this case, for the purpose of preventing the ingression of microorganisms during the course of the connection of the connector members, the two connector members, for example, are sterilized with flame and connected to each other by shrinkage fit.
The dialytic liquid bag is stowed in a packing container in conjunction with a dialytic liquid discharge tube attached to the bag and provided at the leading end thereof with a connector member and is preserved in a wholly sterilized state. Further, this connector member is designed so as to keep the tube in a thoroughly sterilized state even after the cap is attached thereto and the packing container is opened.
The conventional cap for the connector is made of a heat-resistant corrosionproof metal, as illustrated in FIG. 4 and FIG. 5, in the shape of a blind cylindrical cap 5 provided at one end thereof with a tube insertion terminal part 1 having a substantially equal diameter in the direction of the terminal, at the other end thereof with a female insertion terminal part 2 capable of continuously accommodating therein a male insertion terminal part of another connector member (not shown), and in the interior thereof with a stopper 4 comprising a plurality of ridges 4 formed on the lower inner wall surface so as to be inserted into a female connector member B formed in the shape of a short tube possessing a flow path 3 communicating with the aforementioned other connector member (U.S. Pat. Nos. 4,588,402, 4,668,271, and 4,820,288).
When the dialytic solution bag has the conventional cap of this description fitted around the connector member B at the leading end of the flexible tube 6 of the bag, it is set in place in a packing container (such as, for example, a bag of flexible vinyl chloride resin), sealed hermetically, and subjected to about 30 minutes' steam sterilization in an autoclave at 120.degree. C. In consequence of this sterilization in the autoclave, the interior of the dialytic liquid bag is sterilized by the fact that the steam permeating into the container passes through the flexible tube wall and finds its way into the interior of the tube 6 and the interior of the flow path 3 of the connector member B.
The cap intended to protect the connector member at the leading end of the flexible tube is inherently desired to be capable of substantially completely sealing the connector member so as to keep the interior of the connector member and the interior of the tube in an aspectic state until immediately before use. When the dialytic liquid bag using the cap of this nature is sterilized in the autoclave, the steam entrapped in the hermetically sealed bag is condensed after completion of the sterilization. This condensation of steam has the possibility of crushing or flattening the flexible tube and even inducing the phenomenon of blocking of the flexible tube. When the sterilization is carried out with ethylene oxide gas, it is difficult to sterilize the interior of the flexible tube perfectly because this gas does not have enough ability to permeate into the flexible tube.
The problems mentioned above have been heretofore precluded by providing the cap with ribs or recesses adapted to permit passage of air or forming grooves in the connector member. Logically, these measures may well be regarded as disadvantages from the standpoint of maintenance of the aspectic state mentioned above.
Moreover, since this cap is generally made of such thermoplastic resin as polypropylene and, therefore, is thermally shrunken under the influence of the autoclave sterilization, it must be molded in a slightly larger size enough to make up for this shrinkage. It has occurred at times that the cap will slip off the connector member between the time the cap is attached to the connector member and the time the dialytic liquid bag placed in the autoclave undergoes the sterilization.
An object of this invention, therefore, is to provide a novel cap for the connector used in the medical tool.
Another object of this invention is to provide a cap for the connector in the medical tool, which cap has only a small possibility of slipping off the connector member during the course of sterilization.